Stabilized lubricant



Patented Feb. 11, 1941 UNITED STATES PATENT OFFICE ST LUBRICANT Elmer William Oook. New York, N. 1., minor to Tide Water Associated Oil Company, Bayonn v N. 1., a corporation of Delaware 4 No Application September '1, 1939,

. Serial No. 293,101

1:; Claims. (01. era-4a) '10 tions obtaining during use. In some instances,

as in the lubrication of internal combustion engines, high temperatures prevail and thin fllms of the oil are in continued and renewed contact with hot metal surfaces. Strongly oxidizing at- 15 mospheres may be encountered in other services where operating temperatures are the same or may be lower. In the lubrication of steam turbines, the oil temperature is relatively low but contacted metal surfaces or other operating con- 20 ditions may catalyze, promote or permit acid or sludge formation with eventualemulsiflcation due to the presence of water. I br transformer, cable wrapping or other electrical services, the foregoing or other factors may tend to occasion deterioration. I Petroleum hydrocarbon oils may be improved in some respects by refining methods eiiective to remove or convert, at least in'part, certain deterioration inducing constituents normally 30 present therein. 'Reilning with chemicals frequently is employed, as by'extraction with'selective solvents of the character of phenol, liquid sulfur dioxide, nitro-benzene, furiural, and others well known in the art as well as combinations thereof, by clay filtration, or by moderatetreatment with sulfuric acid of less than fuming acid strength. More drastic refining, as by treatment with fuming sulfuric acid, may be resorted to when it is desired to produce highly refined vis- 40 cous hydrocarbon; oils (the so-calied technical white oils) from which substantially all asphaltic constituents have been removed The refined products, however, still are to an undesirable degree susceptibleto oxidation, polymerization, or other chemical phenomena to which may be attributed observed impairment of the oil resulting from or indicated'by acid, gum, and sludge formation, color degradation, inordinate viscosity increase, or other evidence 01 deterioration. 50 Accordingly. it has been p to further improve the service life of various mineral hydrocarbon oils, and in particular lubricating or like oils of petroleum origin, by the incorporation therewith of substances or compounds having an inhibiting or retarding action in one or another respect upon the deterioration of the oil. Many suggestions heretofore have been made in this direction and anumber of compounds advanced for trial as inhibitors some of which in greater or less degree have'proved eifective. Discrepancies in results have been noted, however;

both as to the relative inhibiting efl'ect of a given compound with different oils in overcoming a particular undesired result, and as to the effectiveness of a given inhibitor in preventing 5 different undesired results flowing from the same or diflerent service uses of a given oil. Analogy between different petroleum products and the eflective inhibiting action of various compounds therein does not seem to exist in sumcient degree to provide a reliable basis for predicting the value of an inhibitor in one oil environment from its effect in another. Thus, many compounds effective as anti-gum forming agents'ior cracked gasoline may be wholly without eflect in petroleum lubricating oils. Again, certain inhibitors of value in preventing deterioration of very highly refined turbine oils (the so-called technical white oils) have proved quite ineflective in respect of inhibiting action vides compounds of proven inhibiting action; but 80 it is deemed undesirable and of little practical value to attempt or rely upon any prescribed theory in explanation of observed eilects or results. r

In its broad aspect, the present invention relates to the use of inhibitors which I have discovered to be of marked utility in preventing the deterioration of viscous or relatively viscous petroleum oils (as contrasted with the less viscous or non-viscous distillate petroleum products such as gasoline and kerosene).

More specifically, an important object of the invention is to provide effective inhibitors for lubricating and like oils of petroleum origin; which oils have been subjected in greater or less degree to conventional methods of refining. A further object of the invention is to provide. for the indicated use, inhibitors generally designated as phosphite. esters of phenol sulfides.

It is likewise an object of the invention to imso prove, and to provide improved, lubricating oils by incorporating therewith small amounts of the compounds which I have discovered to be of effective inhibiting action.

Other objects and advantages will appear from the following'description of the invention and the illustrative examples presented hereinafter in order that the invention may be more particularly ascertained. V

The phosphite esters of phenol sulfides found an useful in the practice of the presentinvention are reaction products of a reactive phosphorous compound, such as phosphorous trichloride, and a-phenol sulfide. According to the invention, in a preferred embodiment thereof, the phenol sulflde is first prepared through the inter-reaction of a phenol and a reactive sulfur compound, such as sulfur dichloride. The phenol may be, and preferably is, substituted with such substituent groupings as alkyl, aryl, aralkyl, etc. Among the alkyl substituent groups found particularly.

proportions necessary to effect very substantial inhibiting or stabilizing of the oil in respect of deterioration thereof. Employment, for instance, of phosphite esters of phenol sulfides in proportions as low as 0.1% have proved effective. It will be understood. of course, that larger or smaller proportions of inhibitors may be used as deemed desirable but in general it is contemplated that the practice of the invention will entail the use of amounts of the order of less than 2% and, in the interests of economy, less than 1%. It is not intended that the invention be limited in respect of proportions since the employment of any deterioration and/or corrosion inhibiting proportions is contemplated.

The phosphite esters of phenol sulfides which I have discovered to be of value as inhibitors for lubricating and like petroleum oils are readily soluble in the oil in proportions well in excess of the range indicated above as giving effective stabilizing action. The invention may be practiced, therefore, either by the direct addition of inhibitor to oil in the desired inhibiting proportion or,

as may in many instances be preferable, by preparing a concentrated solution comprising several percent of inhibitor in oil and then adding- .a suitable amount of such concentrate to bulk quantities of oil.

Various tests have been devised and are available by which a comparativeevaluation of oils with respect to deterioration thereof in service may be obtained in a relatively short period of time. Some of these tests are of longer duration than others, but have the advantage of affording a perhaps more reliable laboratory criterion by which to Judge the relative value of various; in-

- hibitors than extremely accelerated tests.

Evidence of the broad utility of inhibitors according to the invention in its intended field of service is afforded by the results of a test method wherein internal combustion engine lubricants comprise the oil environment in which the in-. hibitors function. This test, described below, is one devised in recent years to demonstrate both the-tendency of motor oils to deteriorate per se and their tendency to occasion corrosion of bearing surfaces in internal combustion engines wherein the bearings are formed of or surfaced with cadmium-silver, cadmium-nickel, copperlead and like alloys. The two said tendencies may or may not be related, littlebeing known concerngravity of 29.9, a viscosity at ing the nature of the corrosive action or its causes. It has been observed that motor ofls derived from selected crudes predominantly parafflnic in origin as well as those oils from these or other crudes which have been improved by treatinent with selective solvents, exhibit a marked tendency toward corrosion of the bearings in question, although by other tokens the lubricant is of superior quality and is not corrosive toward bearing surfaces formed of Babbitt metal. It is possible that the high bearing surface temperature existing under service conditions with the newer bearings formed of cadmium-silver and like alloys may be a factor in occasioning the observed deleterious effect of motor oils there- P The aforementioned test, which is known to those conversant with the art as the so-called fUnderwood oxidation testing apparatus is conducted substantially as follows: A freshly sanded copper strip and a'freshly sanded cadmium bearing are supported in achamber in which air may circulate. The copper strip functions as a reproduceableand controlled source of positive catalyst, and the cadmium bearing ail'ords visual, as well as determinable indication as to whether the oil is corrosive. The surfaces are exposed for a period of fifteen hours to a stream of oil sprayed under pressure continuously upon the corrodible areas. The oil is maintained at a temperature of 325 F'. and the spray is so directed as to disperse the oil over the surfaces of the copper strip and cadmium bearing. Means are provided for I given test, thus ice conditions in an engine. Oil deterioration per se is ascertained by observing or determining the neutralization number of the/oil after a test run as well as such factors as the increase in viscosity and carbon residue. The measure of corrosion is taken as the loss in weight of the ,bearing per unit of exposed corrodible surface.

The results obtained utilizing the foregoing test for comparative evaluation with and without an inhibitor according to the invention provide further specific illustration of the value and inhibiting effectiveness of the compounds hereinbefore described. The oil used in the test was a highgrade paraflin base motor oil having an A. P. I.

F. of approximately 295 Saybolt seconds, a viscosity at 210 F. of 54 Baybolt seconds and a carbon residue of 0.44%. A sample of this oil was submitted to test according to a procedure as hereinbefore outlined. The loss in weight per square decimeter due to corrosion of the cadmium bearing was 1.07

rams.

'The used oil after the crease in the Saybolt crease in carbon residue from 0.44 to 8.10, and a neutralization number of 9.8 milligrams KOH per S am of oil. I

There was then inoorporatedwith a fresh supply of the foregoing motor oil an inhibitor according to the invention comprising the phosphite ester of di-p-tertiary-amyl-phenol monosulflde in the amount of 0.5% by weight, and this inhibitor-containing oil then subjected to test according to the indicated procedure. The results indicated a complete suppression of bearing corthe inhibitor, the increase in viscosity at 210 F.

run showed a 44% in viscosity at 210 F., an in- V rosion, no loss in weight of the bearing being observed. Regarding deterioration of the oil itself, substantial benefit resulted from the presence of 70 in internal combustion being nil instead of 44% for the oil without inhibitor, the carbon residue increasing only to 0.93, and the used oil showing a neutralization number of 1.1 milligrams KOH per gram of oil as com- 5, pared with 9.6 in the blank run.

In a further test employing the same initial oil of the foregoing example (having added there- 'to the phosphite ester of di-p-teritary-amylphenol monosulfide in the amount of 0.5%), there 10 was added an additional positive oxidation cata-' lyst in the form of 0.005% FeaOa, based. on the weight of the oil. Even in the presence of this added positive catalyst the inhibited oil exhibited marked tendency to resist oxidation, corrosion l5 and other forms of deterioration. Bearing corrosion was completely suppressed. As to oil deterioration per se, the increase in viscosity at 210 F. was but 5% instead of 44% for the oil without inhibitor, the carbon residue increasing only to 20 1.32, and the used oil showing aneutralization number of 2.1 milligrams KOH per gram of oil' as compared with 9.6 in the blank run. The assembled evidence of allot the foregoin data and results obtained in the several tests 25 demonstrates the advantages attending the use of inhibitors comprising the phosphite esters of aikylphenol sulfides.

I claim: 1. Mineral oil containing a small amount of 30 a phosphite ester of a phenol sulfide.

2. Mineral oil containing a small amount of a phosphite ester of an alkylphenol sulfide.

3. Mineral 011 containing a small amount of the phosphite ester of di-p-tertiary amylphenol 50 8. Mineral oil composition comprising .a viscous hydrocarbonoil normally tending to deterioratein service and having incorporated therewith deterioration inhibiting proportions of a phosphite ester of an alkylphenol sulfide.

55 9. Mineral oil composition comprising a viscous hydrocarbon oil normally tending to deteriorate in service and having incorporated therewith deterioration inhibiting proportions of the phosphite ester of di-p-tertiary amylphenolsulfide.

so 10. The method of lubricating bearing surfaces in internal combustion engines, which bearing surfaces have the corrosion. susceptibility characterizing cadmium-silver cadmium-nickel, and copper-lead alloys. which consists in applying to 65 said bearing surfaces lubricant comprising mineral hydrocarbon oil ha incorporated therein corrosion inhibiting pro rtions of a phosphite ester ofa phenol sulfide.

11. The method of lubri ting bearing surfaces surfaces have corrosion, ceptibiiity characterizing cadmium-silver cadmium-nickel, and copper-lead alloys, which consists in applying to said bearing surfaces lubricant comprising min eral'hydrocarbon oil having incorporated therein corrosion inhibiting proportions of a phosphite 5 ester of an alkylphenol sulfide. Y

12. The method of lubricating bearing surfaces in internal combustion engines, which bearing surfaces have the corrosion susceptibility chars acterizing cadmium-silver. cadmium-nickel, and

copper-lead alloys, which consists in applying tosaid bearing surfaces lubricant comprising mineral hydrocarbon oil having incorporated therein corrosion inhibiting proportions of the phosphite ester of di-p-tertiary amyiphenol sulfide.

13. In the lubrication of bearing surfaces having substantially the corrosion susceptibility characterizing cadmium-silver, cadmium-nickel, and copper-lead alloys, with mineral hydrocarbon oil normally tending to cause substantial and rapid corrosion thereof, the method of inhibiting such corrosion which comprises incorporating with said oil corrosion inhibiting proportions of a phosphite ester of a phenol sulfide. V

14. In the lubrication of bearing surfaces having substantially the corrosion susceptibility characterizing cadmium-silver, cadmium-nickel, and copper-lead alloys, with mineral hydrocarbon oil normally tending to cause substantial and rapid corrosion thereof, the method of inhibiting such corrosion which comprises incorporating with said oil corrosion inhibiting proportions of a phosphite ester of an alkylphenol sulfide;

15. In the lubrication of bearing surfaces having substantially the corrosion susceptibility characterlzing cadmium-silver, cadmium-nickel, and

drocarbon lubricating oil of motor oil character V normally-tending to corrode bearing metal having substantially the corrosion susceptibility characterizing cadmium-silver, cadmium-nickel and copper-lead alloys when continuously applied to the surface thereof for an extended period of time at an oil temperature of 335 F., and a phosphite ester of a phenol sulfide.

17. Mineral oil composition, comprising .a hydrocarbon lubricating oil of motor oil character normally tending to corrode bearing metal havin: substantially the corrosion susceptibility characterizing cadmium-silver, cadmium-nickel and copper-lead alloys when continuously applied to the surface thereof for an extended period of time at an oil temperature of 335 F., and a phosphite ester of an alkylphenol sulfide.

18. Mineral oil'composition, comprising a hydrocarbon lubricating oil of motor oil character normally tending to corrode bearing metal'having substantially .the corrosion susceptibility char- B5 acterizing cadmium-silver, cadmium-nickel and copper-lead alloys when continuously applied to the surface thereof for an extended period of time at an oil temperature of 335'? F., and the phosphite ester of (li p-tertiary anrvlphenol sulfide.

ELMER WILLIAM COOK. 

